The use of Passive Integrated Transponder (PIT) tags which may be embedded in or attached to items to be tracked and accounted for has been widespread for some time. These commonly known PIT tag systems generally comprise one or more antenna coils so positioned as to generate a field of radiated electromagnetic energy within which the tagged item or object must pass. As generally deployed, such systems are used to track and/or count animals within which a PIT tag has been subcutaneously embedded or externally affixed.
As the PIT tag traverses the radiated field of electromagnetic energy, it is energized in a manner known in the art. The PIT tag uses this energy—which is typically stored in a capacitive element—to power a transmission circuit which emits a unique PIT tag identification signal that is detected by the aforementioned antenna element. The identification signal detected by the antenna element is then transmitted to remote processing equipment which decodes the detected signal and uses this decoded information for the purposes of counting, tracking or otherwise maintaining records pertinent to the population of items or animals being tracked by said system.
PIT tags, or transponders, of the type used for object identification, and particularly those which are implantable into living creatures, such as livestock, are well known in the art. Most such PIT tags comprise a coil, which serves as a receiving antenna, for receiving interrogation signals to activate the transponder and for receiving power for its operations. The same antenna is used to transmit the identification signal. An integrated circuit, housed in an art-recognized integrated circuit package, is also provided for performing the circuit functions, including detection of the interrogation signal, conversion of the received signal to DC for powering of the transmitter operations, storage and provision of an identification code, generation of the transmission signal frequency, and modulation of the transmitted signal in accordance with the code and its transmission. The circuit divides the interrogation signal frequency by plural divisors to generate two frequencies which are used to provide a frequency-shift-keyed output signal, the transmission frequency varying in accordance with the stored identification signal. The transponder may be encapsulated in glass or a similarly durable material, as a matter of design choice. It may be supplied together with a disposable cannula for convenient syringe implantation into an animal. Together with essentially conventional interrogator and data storage equipment, a complete animal monitoring system can be provided, suitable for monitoring migratory movements of wild animals as well as laboratory animals, pets and livestock.
PIT tags of the type used for object identification, and particularly those which are implantable into living creatures, such as livestock, are very small and have inherent size restrictions that must be considered in their design and manufacture. Over the years, different size PIT tags were tested and used throughout the industry. Eventually, in the market for animal identification through implantable PIT tags especially, the size became more standardized. Today, one of the more standard sizes in this field is a PIT tag 12 mm long and 2.07 mm wide. Most of the major studies in companion animals and fish applications were carried out with such sized PIT tags. Given such a size standardization, a need in the art has arisen to increase the operating range or performance of the PIT tag without increasing its size.
As described in the prior art, PIT tags have generally been constructed in one of two ways. In the first, the PIT tags are built in subassemblies, such as one subassembly comprising the antenna having loose wire leads and another subassembly comprising the Integrated Circuit (IC) and a capacitor mounted on a Printed Circuit Board (PCB). See, for example, U.S. Pat. No. 5,211,129, which is assigned to the same assignee as the present application, and which is hereby incorporated by reference. The two subassemblies are then electrically and mechanically connected. This approach does provide some advantages, including the use of standard manufacturing machinery as well as the ability to permit design changes quickly and easily during the manufacturing process. However, this approach also has some disadvantages, such as it tends to be labor intensive because much of the assembly of the subcomponents must be done manually, for example, connecting the antenna leads to the IC, and the entire manufacturing process tends to be costly and timely due in part to the number of manufacturing steps involved.
In a second approach, the antenna leads are directly connected to the IC during the manufacturing process. See for example, U.S. Pat. Nos. 5,223,851 and 5,281,855, each of which is incorporated herein by reference. One advantage of such an approach is that the manufacturing process is more fully automated, thus saving time. However, due in part to the small size of the components involved, the machines that directly connect the antenna leads to the IC tend to be expensive and often need maintenance or supervision by a dedicated expert. Further, another disadvantage of this system is that because the antenna leads are connected directly to the IC, it is difficult and expensive to substitute alternate types of ICs or capacitors on the final PIT tag without significant changes in the manufacturing assembly process. Nonetheless, in the prior art the core and IC support subassemblies are not unitary but rather are multi-part assemblies made integral by joining the parts together.
It would therefore be advantageous for a PIT tag to be developed which would alleviate shortcomings of the prior art. The present invention provides a solution.